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Learning Lean, Part II

I've been attending a web based class on Lean development presented by Alan Shalloway. This entry captures some of the more interesting parts. See this previous entry on notes from the first class.

  • Context switching has costs. If you take on three projects at once where each is a month long, you'll take more than three months. An example illustrates the potential irony that this causes. Say you and two others are trying to get a group to do something for you. If you force them to start working on yours (and the others do the same), you'll be worse off than if you allowed them to the three in sequence (even if yours was last). Here's a link to more on the costs of context switching.
  • Batching is bad:
    • Hidden costs of batching: transportation (hand offs / transfer of knowledge), managing the inventory (maintaining that document), storage (lots of open items can overwhelm), capital costs (people costs)
    • Risks of batching: build something you don't need (customer changes mind), inventory becomes obsolete (knowledge degrades quickly; if line is discontinued, all WIP is wasted), huge latency if an error occurs (errors in requirements not discovered until completion)
  • Lean says to shorten time, minimize work in progress, eliminate waste, and do things just in time
  • Waste is anything that doesn't add customer value:
    • Anything that has been started, but not finished
    • Anything that delays development
    • Any extra features
    • Making the wrong thing
  • General categories of waste: inventory, over processing (unnecessary steps), transportation, overproduction (sooner than needed), waiting (lists), unnecessary motion (hand offs), defects, correction, complexity and bureaucracy
  • Some practices:
    • Continuous flow: remove impediments
    • Pull methods: detailed plans can't adapt
    • Value stream: eliminate waste, deliver fast
    • People: respect, challenge, educate
  • Lean principles: Optimize the whole, eliminate waste, build quality in, deliver fast, defer commitment, respect people, create knowledge

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